Adjustable potentiometer with contactor ratchet and central post-securing means for baseplate

ABSTRACT

An adjustable potentiometer of the square-trim-type comprising a case having a compartment formed therein and which is closed by a cover extending thereover. An arcuate resistance element is positioned in the case compartment and has a central post extending upwardly therethrough from the bottom of the case. A circular electrical collector means is operatively rotatably mounted on the post and has a wiper element thereon which is in movable electrical contact with the resistance element. A first lead extends into the potentiometer case and extends upwardly through the post. The collector is rotatably mounted on the upper end of the first lead and includes means for preventing the upward movement of the collector with respect to the resistance element. The collector has spaced-apart teeth which are in threadable engagement with an elongated lead screw rotatably extending into the case. The collector is of flexible construction to permit the deflection or ratcheting of the threads with respect to the threads of the lead screw when the wiper reaches the limits of its travel to prevent damage to the unit. Second and third leads extend into the case and are operatively connected to the ends of the resistance element.

United States Patent Scheel Feb. 1, 1972 ADJUSTABLE POTENTIOMETER WITH [72] Inventor: Louis W. Scheel, Columbus, Nebr.

[73] Assignee: Dale Electronics, Inc., Columbus, Nebr.

[22] Filed: Dec. 18, 1969 [2| 1 Appl. No.: 886,289

52 user 338/174, 333/010. 1 [51] ..H01c 9/02 [58] Field of Search ..338/DlG. 1,118,160,162,

[56] References Cited UNITED STATES PATENTS 3,208,024 9/1965 Enos... ..338/l62 3,353,134 11/1967 Elarde ..338/l60 3,446,085 5/1969 Ginsberg, ..338/DIG. 1 3,470,519 9/1969 Hatch ..338/162 3,518,605 6/1970 Kirkendal] ..338/183 Primary Examiner-Lewis H. Myers Assistant Examiner-Gerald P. Tolin Att0rneyZarley, McKee & Thomte [57] ABSTRACT I case and extends upwardly through the post. The collector is rotatably mounted on the upper end of the first lead and in cludes means for preventing the upward movement of the collector with respect to the resistance element. The collector has spaced-apart teeth which are in threadable engagement with an elongated lead screw rotatably extending into the ,case. The collector is of flexible construction to permit the deflection or ratcheting of the threads with respect to the threads of the lead screw when the wiper reaches the limits of its travel to prevent damage to the unit. Second and third leads extend into the case and are operatively connected to the ends of the resistance element.

1 Claims, 4 Drawing Figures ADJUSTABLE POTENTIOMETER WITH CONTACTOR RATCHET AND CENTRAL POST-SECURING MEANS FOR BASEPLATE limits. Thus, when the wiper arm reaches the limits of its travel, the unit is damaged upon continued rotation of the lead screw. The problem described above was satisfactorily overcome in the copending application but the device of this invention is a significant improvement over the invention of the copending application due to the fact that the instant device is more easily assembled and is more economical of manufacture.

Therefore, a principal object of this invention is to provide an adjustable potentiometer that will not have its internal parts damaged by adjustment beyond its designed capabilities.

A further object of this invention is to provide an adjustable potentiometer having a flexible collector in threadable engagement with the adjustment lead screw, the collector being adapted to ratchet with respect to the threads of the lead screw when the collector and wiper reaches the limits of its travel.

A further object of this invention is to provide an adjustable trimmer potentiometer which is easily assembled.

A further object of this invention is to provide an adjustable potentiometer which is easily fabricated.

A further object of this invention is to provide an adjustable potentiometer that will have a long operating life.

A further object of this invention is to provide an adjustable potentiometer including means to maintain the collector and wiper in electrical contact with the resistance element.

A further object ofthis invention is to provide an adjustable potentiometer which is economical of manufacture, durable in use and refined in appearance.

These and other objects will be apparent to those skilled in the art.

This invention consists in the construction, arrangements, and combination of the various parts of the device, whereby the objects contemplated are attained as hereinafter more fully set forth, specifically pointed out in the claims, and illustrated in the accompanying drawings in which:

FIG. 1 is a perspective view ofthe potentiometer;

FIG. 2 is an enlarged sectional view of the potentiometer as seen along lines 22 ofFlG. 1;

FIG. 3 is a sectional view of the potentiometer as seen along lines 3-3 of FIG. 2 with a portion of the collector cut away to more fully illustrate the invention; and

FIG. 4 is an exploded perspective view of the potentiometer.

The potentiometer of this invention is generally designated by the reference numeral 10 and includes a housing or case 11 having a cover 13 bonded thereon by any convenient means. A compartment 15 is provided in case 11 in which the components of the potentiometer are mounted. As shown in FIG. 2, case 11 has a recessed shoulder area 17 formed therein which receives and supports the cover 13 so that the top of the cover 13 is flush with the upper end or top of the case 11.

A pair of spaced-apart lead screw supports 19 and 21 are provided in case 11 for supporting the lead screw, a T-shaped slot 23 is formed in support 19 while support 21 has a bore 25 formed therein. Bore 25 extends outwardly through wall 26 of case 11 and has an enlarged diameter portion 27 at its outer end. A centrally disposed post 29 extends upwardly from bottom 31 of case 11 and is generally cylindrical in shape prior to the potentiometer components being placed in the compartment 15. A rigid lead 33 extends inwardly into the case 11 as illustrated in FIG. 2 and extends upwardly through the post 29. Lead 33 has its upper end 35 exposed above the upper end 37 of post 29 as shown in FIGS. 2 and 4.

The numeral 39 refers to a plate which is positioned in case 11 so that its central opening 41 receives post 29 extending therethrough. Plate 39 has an arcuate resistance element 43 mounted thereon which may be either wire wound or of the film type. Leads 45 and 47 extend into case 11 and are electrically connected to the spaced-apart ends 49 and 51 of the resistance element 43 respectively. As shown in FIG. 4, the leads 45 and 47 extend horizontally through wall 53 of case 11 and then extend upwardly so that their inner ends extend vertically upwardly through bottom 31 of case 11.

An electrical collector 55 is rotatably positioned above the resistance element 43 and has a tab 57 extending outwardly therefrom adapted to engage the opposite sides 59 and 61 of stop 63 which extends from case 11 into compartment 15 to limit the rotational movement of collector 55 with respect to the resistance element 43. Collector 55 has a wiper element 65 provided thereon which is positioned therebelow and which is adapted to wipe upon the resistance element 43 as the collector 55 is rotated. As seen in FIG. 3, the wiper element 65 is offset with respect to the tab 57. Collector 55 has a central opening 67 which rotatably receives the upper end 35 of lead 33. As seen in FIGS. 2 and 3, collector 55 has a pair of oppositely disposed springlike prongs 69 and 71 which extend upwardly from collector 39 to rotatably engage upper end 35 of lead 33 to prevent collector 55 from moving upwardly on lead 33. Collector 55 is also provided with a threaded" portion 73 defined by spaced-apart protrusions or teeth 75 which extend upwardly from collector 55 adjacent the periphery thereof.

, The lead screw 77 is rotatably mounted in case 11 and has its inner end 79 rotatably mounted in slot 23 and has its other end 81 rotatably mounted in bore 25. An O-ring 89 embraces lead screw 77 in enlarged diameter portion 27 of bore 25 to seal the interior of the case 11 from the atmosphere. Lead screw 77 has a conventional head portion 91 positioned outwardly of wall 26 of case 11 to permit the lead screw 77 to be rotatably adjusted by means ofa screwdriver or the like. Load screw 77 has a threaded portion 93 which threadably engages the teeth 75 of collector 55 as seen in FIGS. 2 and 3.

Cover- 13 is provided with an ear 94 which extends downwardly therefrom into compartment 15 so that its lower end engages collector 55 as illustrated in FIG. 2 for purposes of balancing the collector 55. Ear 94 offsets the leverage applied to the collector 55 by the lead screw 77. Cover 13 is also provided with a downwardly extending arcuate lug 96 which is positioned over portion 98 of lead screw 77 (FIG. 2).

The potentiometer is assembled in the following manner. The plate 39 with the resistance element 43 thereon is positioned in the compartment 15 so that the bottom of the late 39 engages or rests upon the bottom 31 of case 11 and so that the inner ends of the leads 45 and 47 electrically engage the opposite ends of the resistance element 43. A downward com-v pressive force is then applied to the top 37 of post 29 so that the post 29 is deformed from the cylindrical shape of FIG. 4 to the mushroom shape of FIG. 2 which causes a portion of the post 29 to be deflected outwardly over the recessed area 95 of plate 39 to positively maintain the plate 39 in the position of FIG. 2.

The collector 55 is then inserted downwardly into the compartment 15 until the bottom surface of the collector 55 engages the upper surface of the post 29. The wiper element 65 is in electrical engagement with the resistance element 43 in such a position and the springlike prongs 69 and 71 permit the collector 55 to be snapped on the upper end 35 of the lead 33. The prongs 69 and 71 maintain the collector 55 in the position of FIG. 2 and insures that the wiper 65 will be maintained in proper electrical contact with the resistance element 43.

Lead screw 77 is then inserted through bore 25 and end 79 thereof is dropped into" slot 23. In this position, threads 93 threadably engage the teeth 75. Cover 13 is then mounted on the case ll and bonded thereto by conventional means. With the cover 13 installed, ear 94 balances the collector 55 as previously discussed and lug 96 maintains lead screw 77 in position.

In operation, the lead screw 77 may be rotated to adjust the potentiometer by use of a conventional screwdriver. The rotation of lead screw 77 will cause collector 55 to be rotated due to the engagement of teeth 75 with the threads 93 of the lead screw 77. The rotation of collector 55 causes the wiper element 65 to wipe along the resistance element 43 so that the resistance in the electrical circuit can be selectively varied in conventional fashion. The tab 57 will engage the opposite sides 59 and 61 of stop 63 when the collector has reached the limits of its travel with respect to the resistance element 43 respectively. When the wiper 65 has reached the limits of its travel, the tab 57 will be engaging either of the sides 59 or 61 of the stop 63. When the tab 57 is engaging the stop 63, the continued rotation of the lead screw 77 will cause the ratcheting of the teeth 75 with respect to the threads 93. THe flexible characteristics and design of the collector 55 is such that the teeth 75 will be deflected downwardly or ride under the threads 93 upon the continued rotation of the lead screw 77 to provide a ratcheting effect. Thus, the internal components of the unit will not be damaged due to continued rotation of the lead screw since the teeth 75 will ratchet which means that collector 55 and wiper 65 will not be rotated. It can be appreciated that the teeth 75 can be indefinitely ratcheted with respect to the lead screw without causing damage to either of the lead screw or collector 55.

The design of the potentiometer permits the potentiometer to be easily fabricated and to be easily assembled. The components of the potentiometer are simply inserted downwardly into the compartment and the components are maintained in the proper position therein due to the compression of the post 29 and due to the prongs 69 and 71 maintaining such relative positions.

Thus it can be seen that an easily fabricated and assembled potentiometer has been provided which insures that the components thereof will not be damaged by adjustment beyond its designed capabilities.

The components of the unit are constructed of conventional materials while collector 55 is preferably constructed of No. Berylco.

Thus, it can be seen that the potentiometer accomplishes at least all of its stated objectives.

Iclaim:

1. In an adjustable potentiometer,

a housing,

a compartment in said housing,

an arcuate resistance element in said compartment,

said housing having an integrally formed central post means extending upwardly into said compartment centrally through said resistance element,

an electrical collector means operatively rotatably mounted on said post means above said resistance element, said collector means having a wiper mounted thereon in movable electrical contact with said resistance element,

an elongated lead screw rotatably mounted in said housing and having a threaded portion normally in threaded engagement with said collector means whereby rotation of said lead screw will normally cause the rotation of said collector means,

said collector means being flexible and having thread means thereon adapted to engage the threads of the threaded portion of said lead screw,

the flexible characteristics of said collector means permitting said thread means of said collector to be deflected and ride over the threads of said lead screw thereby providing a ratcheting effect when said lead screw is continued to be rotated after said wiper reaches the limits of its travel, a first lead extending upwardly through said central post means, said first lead being of rigid construction and having a cylindrical shape,

said collector means being rotatably mounted on said first lead and being in electrical contact therewith,

and second and third leads operatively electrically connected to said resistanceelement, I said resistance element being mounted on a flat plate. said central post having an upper end portion extending outwardly over a portion of said flat plate to maintain said flat plate in position in said compartment. 

1. In an adjustable potentiometer, a housing, a compartment in said housing, an arcuate resistance element in said compartment, said housing having an integrally formed central post means extending upwardly into said compartment centrally through said resistance element, an electrical collector means operatively rotatably mounted on said post means above said resistance element, said collector means having a wiper mounted thereon in movable electrical contact with said resistance element, an elongated lead screw rotatably mounted in said housing and having a threaded portion normally in threaded engagement with said collector means whereby rotation of said lead screw will normally cause the rotation of said collector means, said collector means being flexible and having thread means thereon adapted to engage the threads of the threaded portion of said lead screw, the flexible characteristics of said collector means permitting said thread means of said collector to be deflected and ride over the threads of said lead screw thereby providing a ratcheting effect when said lead screw is continued to be rotated after said wiper reaches the limits of its travel, a first lead extending upwardly through said central post means, said first lead being of rigid construction and having a cylindrical shape, said collector means being rotatably mounted on said first lead and being in electrical contact therewith, and second and third leads operatively electrically connected to said resistance element, said resistance element being mounted on a flat plate, said central post having an upper end portion extending outwardly over a portion of said flat plate to maintain said flat plate in position in said compartment. 